Red herrings and zebras and TB, oh my! Unexpected bone marrow presentation of Mycobacterium tuberculosis

Abstract Introduction/Objective Epithelioid granulomas are uncommon and non-specific findings in bone marrow samples, and should prompt additional testing for appropriate diagnosis and treatment, especially in the immunocompromised patient. The differential diagnosis for bone marrow granulomas includes infections, neoplasia, autoimmune disease, sarcoidosis, and drug/therapy reaction. Although bone marrow workup to delineate the cause of granulomas should include staining to rule out both infection and lymphoma, morphologic review is often inconclusive. Final diagnosis requires clinical consultation and additional testing. Methods/Case Report A 76-year-old male was admitted to the hospital from the emergency department for a level 2 trauma after being found on the ground ~3 hours after a fall. The patient reported a recent increasing frequency of falls with associated weakness, as well as an almost 30 lb weight loss over the last 3.5 months and low grade fevers over several weeks. His past medical history was significant for treatment for urothelial carcinoma with transurethral resection and BCG therapy, hypertension, coronary artery disease, and peripheral vascular disease. Imaging showed hepatosplenomgaly, suspicious for early cirrhosis, and mild peripancreatic lymphadenopathy. Initial laboratory abnormalities demonstrated mild anemia, low albumin, and mild increase in ALT, AST, and alkaline phosphotase. Initial Infectious Diseases workup was negative for causative etiology (blood cultures, tick-borne parasites, and respiratory pathogens). Patient symptoms did not improve and cytopenias worsened. A bone marrow biopsy showed multiple non-necrotizing epithelioid granulomas. Despite low clinical concern for infectious etiology, mycobacteria blood culture isolated Mycobacterium tuberculosis complex. Final results were available 112 days after specimen collection. Results (if a Case Study enter NA) NA Conclusion Although tuberculosis is commonly associated with granulomatous pathology, infection is very uncommon in North American patients who have not traveled and alternative diagnoses might initially be favored. A high suspicion for mycobacterial infections is essential for diagnosis even in low-incidence populations with no known exposure or risk factor(s).